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The initial growth stage of C(60) thin film on graphite substrate has been investigated by scanning tunneling microscopy in ultrahigh vacuum at room temperature. The C(60) layer grows in a quasi-layer-by-layer mode and forms round, monolayer high islands on the graphite surface. The islands are confined by terraces on the graphite surface and the mobility of C(60) fullerenes across steps is low in all layers. The second and all subsequent layers adopt a fractal-dendritic shape, which was confirmed by calculating the fractal dimension (D=1.74 prior to island coalescence) and is in agreement with a diffusion limited aggregation. The profound differences between the growth of C(60) layers on graphite (first layer) and on C(60) surfaces (second and higher layers) are caused by the restriction of the C(60) mobility on the highly corrugated fullerene surfaces. The orientation of the fractal islands follows the hexagonal symmetry of the densely packed (111) surface of the fullerene lattice, which introduces a bias in the direction of molecule movement. The differences in surface topography on the nanoscale determine the mode of film growth in this van der Waals bonded system.

The molecular-level processes responsible for fractal-dendritic growth of second-layer C60 islands on large and compact first-layer C60 islands deposited on graphite substrate are investigated by a combination of scanning tunneling microscopy (STM) and kinetic Monte Carlo (kMC) simulations. Molecular dynamics (MD) simulations are performed to determine the activation barriers and jump rates for diffusion of C60 molecules on a C60 layer. The rates of the thermally activated processes, determined in MD simulations, are used in kMC simulations performed to explore the connections between the elementary growth mechanisms and the shapes of the growing islands. The geometry of the underlying substrate is found to result in the formation of two characteristic molecular arrangements along the edges of the growing islands (A-step and B-step on a close-packed surface). The difference in the molecular mobility along the A-step and B-step configurations, along with the difference in the probability of a C60 molecule to diffuse from a corner of an island to A-step or B-step edges of the island, are identified as key factors responsible for the formation of characteristic triangular shapes of the fractal islands and their orientation with respect to the underlying surface structure. The fractal shapes of the second-layer C60 islands predicted in kMC simulations are in a good agreement with STM images taken under comparable deposition conditions.

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Intercalation of C60 molecules at the graphene-substrate interface by annealing leads to amorphous and crystalline structures. A comparison of topography and electronic structure with wrinkles and moiré patterns confirms intercalation. The intercalated molecules imprint a local strain/deformation on the graphene layer whose magnitude is controlled by the intermolecular distance. The crystalline intercalated structure exhibits a superlattice peak in the local density of states. This work provides control of local strain in graphene.